What joke is the penguin telling?

Explore the Antarctic alone. He met a penguin. He asked, "What do you do every day?" Answer: "Eat and sleep, Big Doudou!" He walked on and met two penguins. "What do you do every day?" "Eat and sleep and beat peas." He met the third penguin. "What do you do every day?" "Eat, sleep and fight peas!" In this way, the man met the hundredth penguin. "What do you do every day?" "Eat and sleep!" "Why not fight peas?" "Because I am Doug! ! "